Gas turbines are used in a variety of applications. Gas turbines have a compressor section for compressing inlet air, a combustion section for combining the compressed inlet air with fuel and oxidizing that fuel, and a turbine section where the energy from the hot gas produced by the oxidation of the fuel is converted into work. Usually, natural gas (mostly methane), kerosene, or synthetic gas (such as carbon monoxide) is fed as fuel to the combustion section, but other fuels could be used. The rotor, defined by a rotor shaft, attached turbine section rotor blades, and attached compressor section rotor blades, mechanically powers the compressor section and, in some cases, a compressor used in a chemical process or an electric generator. The exhaust gas from the turbine section can be used to achieve thrust or used as a source of heat and energy. In some cases, the exhaust gas is simply discarded.
Water injection or steam injection within the combustion chamber is a technology to reduce or limit thermal NOx formation by reducing the combustion turbine flame temperature. Water added at the compressor inlet when the gas turbine is operating under full load also augments the power output capability of a gas turbine above the output achievable with normally humidified air. Such an arrangement is referred to as “wet compression,” such as disclosed in U.S. Pat. No. 4,841,721 to Patton et al. Wet compression enables power augmentation in gas turbine systems by reducing the work required for compression of the inlet air. This thermodynamic benefit is realized within the compressor of a gas turbine through latent heat intercooling, in which water (or some other appropriate liquid) is added to the air inducted into the compressor and cools that air, through evaporation, as the air with the added water droplets are being compressed.
Additional fuel flow is generally required to raise the temperature of the cooled air/steam mixture discharged from the compressor to the firing temperature of the gas turbine as compared to otherwise equivalent dry air compression. However, a decrease in compressor discharge air temperature can result in a destabilization of the combustion flame. Combustion stabilization can be achieved by retuning the combustion system, however this typically results in increased NOx emissions. What is needed is a method for combustion stabilization for wet compression applications that does not increase NOx emissions.